Java interface

Associative arrays in scripting languages

Many programming languages, particularly those designed for scripting
support associative arrays implemented with hashes.
The implementation technique is so common that the associative array
is often called a “hash%rdquo; by programmers
of those languages.

Perl

Perl was one of the first programming languages to provide
hashes as a built-in datatype. In fact, one of the
main reasons for programmers converting to Perl in the early-90’s
was its support for hashes.

In Perl a hash can be created and initialized with a single statement.

%numSeats = (
CSCI181 => 18,
'HUM 224' => 180
) ;

Once an hash has been defined, it can be accessed with a minor
modification of the usual array syntax.

$numSeats{'HUM 224'} = 10 * $numSeats{'CSCI181'} ;

Python

Python implements hashes with the dictionary
and uses the same syntax for accessing hash and array elements.

JavaScript

Note that hashes can be accessed using
C/Java style field selectors in addtional to normal
array lookup.

JavaScript, like PHP, even implements regular arrays with hashes.
The array index V[202] will be implemented
as the hash index V["202"].
In web scripting languages, these minor inefficiences can be ignored.

Java and C++

Both the C++ Standard Template Libary (STL) and the
Java collection framework (JCF) has a
Map that corresponds to a hash table.

Because C++ supports
operator
overloading, it is possible to overload the array index
operator [ ] and use the array lookup syntax
in surprising ways.